DESCRIPTION

setjmp()
and
longjmp(3)
are useful for dealing with errors
and interrupts encountered in a low-level subroutine of a program.
setjmp()
saves the stack context/environment in env for
later use by
longjmp(3).
The stack context will be invalidated
if the function which called
setjmp()
returns.

sigsetjmp()
is similar to
setjmp().
If, and only if, savesigs is nonzero,
the process's current signal mask is saved in env
and will be restored if a
siglongjmp(3)
is later performed with this env.

RETURN VALUE

setjmp()
and
sigsetjmp()
return 0 if returning directly, and
nonzero when returning from
longjmp(3)
or
siglongjmp(3)
using the saved context.

CONFORMING TO

NOTES

POSIX does not specify whether
setjmp()
will save the signal mask.
In System V it will not.
In 4.3BSD it will, and there
is a function _setjmp that will not.
By default, Linux/glibc follows the System V behavior,
but the BSD behavior is provided if the
_BSD_SOURCE
feature test macro is defined and none of
_POSIX_SOURCE,
_POSIX_C_SOURCE,
_XOPEN_SOURCE,
_XOPEN_SOURCE_EXTENDED,
_GNU_SOURCE,
or
_SVID_SOURCE
is defined.

If you want to portably save and restore signal masks, use
sigsetjmp()
and
siglongjmp().

setjmp()
and
sigsetjmp()
make programs hard to understand
and maintain.
If possible an alternative should be used.